Magnetic materials



July 19; 1960 K. KNOX 2,945,744

MAGNETIC MATERIALS Filed Feb. 14, 1958 I :REFR/GERA T/ON SPACE 2:, PUMP INPUT f; OUTPUT //v VENTOR K. KNOX ATTORNEY magnetic.

MAGNETIC Kerro Knox, Summit, N.'J., assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation, of NewYork Filed Feb. 14,1958, Ser. No. 715,415

-4 Claims. (Cl. 23.-50)

This invention relates to magnetic materials, and more particularly to ferrimagnetic fluoride compounds.

- Ferromagnetic materials, which include the elements iron, nickel and cobalt, are madeup of domains. The atoms within each domain behave like magnetic dipoles, and are aligned parallel to one another even in the absence of an applied magnetic field. This alignment is known as spontaneous magnetizat ion, and is the basic characteristic feature of ferromagnetic materials.

, Ferrjmagnetic materials (of which ferrites are the prototypes) also' have a domain structure and exhibit spontaneous magnetization. These materialshave their magnetic dipoles. arrangedintwo or more sub-lattices of crystallographically difierent sizes. The exchange forces between thelmagneti'c dipoles in the sub-lattices are negative, i.e., the magnetic moments of the sub-lattices tend to align in an antiparallel manner. When the vector sum of the "magnetic moments of the sub-lattices is not'zero, either because the'inagnetic moments of the sub-lattices are different in magnitude and/or because themagnetic momentsyarenotstrictly antiparallel, spontaneous magnetization results and the material is ferri- Ferrimagnetic materials are utilized in a variety of microwave communications devices, forexample, circulators,.isolators,f attenuators and amplifiers. More specifically, these materials may be employed as theac'tive elements of low noise parametric amplifiers of the type described by H. Suhl in the Physical Review, volume 106, page 384, Apr. 15, 1957, and by him in The Journal of Applied Physics, volume 28, page 1225, November 1957. An illustrative amplifier device of the Suhl type is shown in the accompanying drawing. The device includes suitable means (not shown) for supplying a steady external magnetic field (represented in the drawing by a vector H) to a block member having a cover plate 11, which block 10 and plate 11 define a reaction zone.

The block 10 includes two intersecting resonators, the first of which is of the wave guide type and comprises a rectangular channel 12 whose input end is connected to a source 13 of pumping power at a frequency f The second resonator of the illustrative device shown in the drawing is of the strip-line type and comprises a channel 16 extending at right angles to the channel 12. Suitably supported within the channel 16 is a thin conductive member 17, the elements 16 and 17 comprising a strip-line wave supporting structure 16-17.

A wave at h, the frequency to be amplified, is launched upon the strip-line assembly 1617 from a source 20 by means including a probe 21.

The amplified output signal may be taken from the line assembly 16-17 by a probe 22 which is connected by suitable means including a-filter 27 to a load 24.

Nonlinear coupling between the energy supported in the resonators 12 and 16-17 is provided by two bodies 25 and 26 which may advantageously be formed from United a States Patent O 2,945,744 Patented July 19, 1960 Hit? a material made in accordance with aspects of the principles of this invention.

The dashed lines in the drawing schematically represent a refrigeration space within which portions of the constituent materials therefor.

7 Another object of this invention is an improved class of ferrimagnetic materials.

A more specific object of the present invention is a class of ferrimagnetic fluoride compounds.

These and other objects of the present invention are realized in compounds having the formula Na X F .wherein X represents atrivalent metallic ion chosen from a group consisting of the following: chromium, cobalt, copper, iron, manganese, molybdenum, nickel, palladium, rhodium, tantalum, titanium and vandium.

' Each member of the group above is a transition element whose trivalent ion exhibits a magnetic moment and further, whose trivalent oxidation state is known to exist in fluoride compounds.

One specific illustrative embodiment of the present in- -vention is a compound having the formula Na Fe F In a specific process for making this embodiment, there 'were'mixedtogether the compounds NaF and FEF I in the mole ratio of SNaF to 3FEF which corresponds to the stoichiornetric proportions. This mixture, in an ing resulted in the formation of the compound Na Fe F which is a red-brown material.

When stoichiometric proportions of the ingredients NaF and FEF were mixed together, .there was obtained the compound NagFe F substantially free of other residue. However, when proportions other than stoichiometric (in the composition range 70 mole percent NaF with 30 mole percent FeF to 50 mole percent NaF with 50 mole percent FeF were used, the product was a polyphase material made up of a transparent red-brown phase, Na Fe F and other phases.

In a reaction which produces the red-brown and other phases, the desired red-brown phase may be separated out by a mechanical separation process which includes grinding the material obtained from the reaction into relatively small pieces (more specifically, pieces having largest dimensions across falling in the range 1 to 50 thousandths of an inch), and then picking out therefrom the transparent red-brown elements. Alternatively, the desired red-brown elements may be separated from the unwanted pieces by cooling the ground material to a temperature below the Curie point of the red-brown phase, and then attracting the desired elements with a magnet.

It is noted that any other non-reacting vessel, for example, a graphite one, and any other inert atmosphere, for example, one of nitrogen or argon, may be employed in the above-recited method.

Additionally, it is noted that the specified temperature of 700 degrees centigrade is not critical. It is feasible, for example, to employ lower temperatures, in which cases the times required for a given reaction would be increased over that recited above.

Similarly, higher temperatures than that specified may be employed. It has not, however, been found particularly advantageousto utilize much higher temperatures.

Low temperature magnetization measurements down to 1.7 degrees Kelvin have demonstrated that the compound .Na Fe F is ferrimagnetic, having a Curie temperature of about 80 degrees Kelvin. (Microwave amplifiers of the Suhl type may advantageously'be operated at temperatures below this relatively low Curie point, thereby enhancing the low noise characteristics thereof.)

Further investigations of the properties of the compound Na Fe F indicated that the resistivity of a pellet thereof is greater than ohm'centimeters, which relatively high electrical resistivity is particularly advantageous for adapting the materials for use in the microwave devices above-mentioned. I

The method described above is suited for making nine other specific illustrative embodiments of the present invention, namely, Na Co F (formed from NaF and CoF Na Cr F (formed from NaF and CrF Na Mn F (formed from NaF, and MnFa), Na Mo F (formed from NaF and M01 Na Pd F (formed from NaF and PdF Na Rh F (formed from NaF and RhF Na Ta F (formed from NaF and TaF Na Ti F (formed from NaF and TiF and Na V F (formed from NaF and VF NaF and the trifluorides of cobalt and manganese are commercially available compounds. The other trifluoride compounds, namely, CrF FeF MoF PdF RhF TaF TiF and VF may advantageously be prepared in accordance with the procedures given in Fluorine and Its Compounds, by R. N. Haszeldine and A. G. Sharpe, Methuen, London, 1951, at the following pages respectively: 51, 52, 53, 56, 56, 59, 50 and 50.

The compounds Na Cu F and Na Ni F require for their synthesis methods different from that recited above. The method for preparing the compound Na Cu F comprises the following steps: (1) combining the commercially-available compounds NaCl and CuCl so that sodium and copper exist in the mixture in the proportion 5:3 by mole ratio; (2) containing the mixture in an inert vessel, such as a nickel boat, and then passing elementary fluorine over these compounds in a reaction zone heated to 700 degrees centigrade, thereby converting the chloride compounds to fluoride compounds, oxidizing the copper ions from their +1 to their +3 states, and reacting NaF with the trivalent copper ions and available fluoride ions to form Na Cu F Similarly, the method for preparing the compound Na Ni F comprises the following steps: (1) combining NaCl and NiCl (the latter is formed by heating in a Well-known manner the commercially-available compound NiCl '6H O) so that sodium and nickel exist in the mixture in the proportion 5:3 by mole ratio; (2) containing the mixture in. an inert vessel, such as a nickel boat, and then passing elementary fluorine over these compounds in a reaction zone heated to 700 degrees centigrade, thereby converting the chloride compounds to fluoride compounds, oxidizing the nickel ions from their +2 to their +3 states, and reacting NaF with the trivalent nickel ions and available fluoride ions to form Na Ni F It is to be understood that the above-described arrangements are illustrative and not restrictive of the principles of the present invention. Other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. A class of ferrimagnetic materials having the formula Na X F wherein X is a trivalent metallic ion chosen from a group'consisting of chromium, cobalt, and iron ions.

2. A ferrimagnetic material having the formula Na Fe F 3. A ferrimagnetic' material having the formula Na5CO F14.

4. A ferrimagnetic material having the formula Na Cr F References Cited in the file of this patent UNITED STATES PATENTS 2,723,182 Sibert Nov. 8, 1955 2,793,097 McKenna -May 21, 1957 2,825,765 Marie Mar. 4, 1958 OTHER REFERENCES Chemical Abstracts, vol. 18, page 2478; vol. 40, cols. 1637, 7038.

A Comprehensive Treatise on Inorganic and Theoretical Chemistry, by Mellor, vol. 9, pp. 797, 916-918 (1929); vol. 11, pp. 363, 364, 610 (1931); vol. 14, p. 9 (1935); vol. 15, p. 658 (1936), pub. by Longmans, Green, London. 

1. A CLASS OF FERRIMAGNETIC MATERIALS HAVING THE FORMULA NA5X3F14, WHEREIN X IS A TRIVALENT METALLIC ION 